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Atmospheric pressure plasmas for surface modification

Abstract

Many methods are currently used for the production of silicon oxide films, most have drawbacks associated with high temperatures and the requirement for a vacuum. Atmospheric pressure plasma treatment can address some of these difficulties. Air silent discharge treatment of spin-coated organo-silicon compounds resulted in substantial oxidation. The depth and morphology of the oxidised region was found to depend on the structure of the precursor. Condensation of substituted chlorodisilanes (SCDS) onto polymer surfaces yielded polysiloxane-like layers. Upon atmospheric pressure plasma oxidation these gave rise to SiOx rich films which exhibited gas barrier, and readily underwent reaction with conventional chlorosilane coupling reagents. Dielectric barrier discharge and atmospheric pressure glow discharge (APGD) modification of polydimethylsiloxane (PDMS) containing polyethylene blends led to the formation of wettable, SiOx rich coatings. The hydrophobic recovery, SiOx content, reactivity and topography of the oxidised films was found to depend on the architecture of the PDMS additive. The limited depth penetration of plasma oxidation was thought to limit its potential as a gas barrier technology. The development of a novel APGD plasma reactor equipped with an ultrasonic nozzle enabled the creation of thick coatings from cyclotetrasiloxane monomers. Control of the feed gas allowed the rapid deposition of both hydrophobic polysiloxane-like films and hydrophilic SiOx gas barrier coatings. The APGD deposition methodology was extended to the creation of organic plasma polymers. The resultant polyacrylic acid and 1H, 1H, 2H,- perfluoro-1-octene films were highly functionalised and exhibited properties comparable with their conventionally manufactured counterparts.